Category

Published on

Abstract

A laboratory experiment was performed to investigate the three-dimensional turbulence and kinematic properties that
develop due to a breaking solitary propagating over an irregular shallow water bathymetry. The bathymetry consisted
of a deep water region connected to a shallow shelf via a relatively steep slope. The offshore boundary of the shelf
break varied in the longshore direction, such that the shelf had a triangular shape in plan view, with the widest part of
the shelf along the basin centerline. Free surface elevations and fluid velocities were measured using wave gauges
and three-dimensional acoustic-Doppler velocimeters (ADVs), respectively. From the free surface elevations the
evolution and runup of the wave was revealed; while from the ADVs, the velocity and turbulent energy was
determined and specific turbulent events and coherent structures were indentified. It was found that significant
shoaling was confined to areas with gentler sloping bathymetry near the basin side walls and the runup varied weakly
in the alongshore direction. The runup was characterized by a refraction-generated jetting mechanism caused by the
convergence of water mass near the basin centerline. The jetting mechanism caused the greatest cross-shore
velocities to be located near the basin centerline. The greatest turbulent events were well correlated to borefronts, of
which there were four, caused by the leading wave, beach reflections, and shelf-trapped oscillations. Along the shelf
break, a large, shallow-water eddy developed which was found to have a peculiar three-dimensional flow field, where
maximum velocity components were found at mid-depth.